#203 create transport only once

only-once.patch

diff --git a/uvloop/sslproto.pxd b/uvloop/sslproto.pxd
index 30efa5c..e3f79a2 100644
--- a/uvloop/sslproto.pxd
+++ b/uvloop/sslproto.pxd
@@ -27,6 +27,7 @@ cdef class SSLProtocol:
         object _waiter
         object _loop
         _SSLProtocolTransport _app_transport
+        bint _app_transport_created
 
         object _transport
         bint _call_connection_made
diff --git a/uvloop/sslproto.pyx b/uvloop/sslproto.pyx
index ab02252..82b0015 100644
--- a/uvloop/sslproto.pyx
+++ b/uvloop/sslproto.pyx
@@ -250,6 +250,7 @@ cdef class SSLProtocol:
         self._loop = loop
         self._set_app_protocol(app_protocol)
         self._app_transport = None
+        self._app_transport_created = False
         # transport, ex: SelectorSocketTransport
         self._transport = None
         self._call_connection_made = call_connection_made
@@ -303,7 +304,10 @@ cdef class SSLProtocol:
 
     def _get_app_transport(self):
         if self._app_transport is None:
+            if self._app_transport_created:
+                raise RuntimeError('Creating _SSLProtocolTransport twice')
             self._app_transport = _SSLProtocolTransport(self._loop, self)
+            self._app_transport_created = True
         return self._app_transport
 
     def connection_made(self, transport):